(1) Field of the Invention
The present invention relates to a storage container for precision substrates which accommodates, stores, transfers, carries or transports semiconductor wafers or precision substrates such as mask glasses, and can be connected to a standardized mechanical interface apparatus for machining precision substrates (SMIF: Standard Mechanical Interface) or FIMS (Front-opening interface Mechanical Standard).
(2) Description of the Prior Art
Conventional storage containers for precision substrates comprise, as shown in FIG. 1 and FIG. 2, a pod case 1 for accommodating a plurality of semiconductor wafers (hereinafter, referred to as "wafers"), a pod door 12 for detachably covering the front opening of the pod case 1, and a bottom plate 23 attached to the bottom face of the pod case 1. The pod case 1 is formed in a front-opening box structure, with a plurality of engagement holes 6 formed on the upper and lower sides of the front inner periphery, respectively. A rear retainer 7 is attached on the inner back face of the pod case 1, and opposed substrate supports 8 are respectively attached on the inside both sides, these rear retainer 7, and a pair of substrate supports 8 aligning a plurality of wafers W in the vertical direction.
The pod door 12 has an opening/closing lock mechanism 15 built therein for vertically moving a plurality of latch plates 21 based on the rotation operation of disks 19. Each latch plate 21 of the opening/closing lock mechanism 15 has an engagement pawl 22 formed thereon which appears and disappears from/to a through hole 12a on the pod door 12. Each engagement pawl 22 fits and engages with each engagement hole 6, thereby the pod door 12 is firmly fitted and attached on the front of the pod case 1 so as to cover the front face.
In the above configuration, when wafers W are accommodated, a plurality of wafers W are aligned and accommodated in the pod case 1, and the pod door 12 is fitted to the opening front face of the pod case 1, as well as the opening/closing lock mechanism 15 is operated to be locked by means of unillustrated pod opener, hence the plurality of wafers W are accommodated in the storage container for precision substrates in an airtight condition.
Moreover, when the wafers W are to be processed, the storage container for precision substrates is positioned and set, for example, on a carrier stage of unillustrated handling apparatus, together with unillustrated open cassette. Then, the opening/closing lock mechanism 15 on the pod door 12 is operated to be released by means of the pod opener to detach the pod door 12 from the opening front of the pod case 1. After the storing state or the like of the plurality of wafers W is confirmed, they are pulled out from the bottom in turn by a transfer mechanism of the handling apparatus, and transferred to an open cassette of the other carrier stage from the bottom.
In processing and machining of the wafers W, it is necessary to accurately identify and recognize the information regarding the variety of wafers W and the storage container for precision substrates. To realize this identification, as shown in FIG. 3 and FIG. 4, there has been conventionally adopted a method of either (1) adhering an identification code seal 37 on the back of the pod case 1, or (2) integrally forming a pocket on the back of the pod case 1 and putting an identification plate 29 in the pocket 38.
As this type of related prior arts, there can be mentioned Japanese Utility Model Application Laid-open Hei 6 No. 77247, Japanese Utility Model Application Laid-open Hei 5 No. 50740, Japanese Utility Model Application Laid-open Sho 64 No. 48032, Japanese Patent Application Disclosure Sho 61 No. 502994, Japanese Patent Application Disclosure Sho 63 No. 503259, Japanese Patent Application Disclosure Sho 63 No. 500691, Japanese Patent Publication Hei 6 No. 38443, Japanese Patent Publication Hei 7 No. 46694, and Japanese Patent Application Laid-open Hei 8 No.279546.
With the conventional storage container for precision substrates, the wafers W and the storage container for precision substrates are identified in the manner as described above. Either method may be adopted, however, there have been various problems as described below. First, in the method (1), when the storage container for precision substrates is cleaned or rinsed, the wafers W are likely to deteriorate its quality due to the influence of an adhering agent. As a measure against the quality deterioration, there can be considered a method that the cleaning time is extended, or inferior products are rejected. With this method, however, there is caused another problem that the productivity drops. Moreover, when the storage container for precision substrates is collected, cleaned and reused, the number of process is increased for putting new identification code seals 37 using the adhering agent, and the cleaning time tends to become long.
In the case of the method (2), since the pod case 1 and the pocket 1 are integrally formed, there are such problems that the structure of the mold becomes very complicated, and the cost cannot be maintained or controlled. Moreover, when the storage container for precision substrates is injection-molded, the back face of the pod case 1 forms a portion where a gate is provided. Therefore, molding the pocket 38 in this portion leads to restriction of the position of the gate or decrease in the number of gates, making the molding condition worse. Furthermore, in molding the pocket 38, it has to be constructed in a nesting structure with the mold being a separate part, which leads another problems that cooling becomes instable, and that inferior products may be produced.
Furthermore, when a plate holding portion of the pocket 38 is molded, it causes resistance when the formed article is released from the mold. Therefore, it is necessary to attach a slide mechanism in the nesting portion where the plate holding portion is formed to release the plate holding portion from the molded article to remove the resistance. In this case, the slide mechanism is likely to be affected by the heat of the resin to be filled, due to its position near the gate. Hence, there is caused another problem that the slide mechanism may malfunction due to the thermal expansion or the like to decrease the durability.